In Mystery caches there is a box to enter the final coordinates (is this new?).
If you enter a set of coordinates that are west of the meridian and use a lower case W, when you hit save it becomes an E which kinda moves the location a touch.
e.g if I enter "n 51 01.950 w 001 30.250" in the box on a cache, select Solved from the dropdown and hit save I get "N 51° 01.950 E 001° 30.250"
I just tested and a lower case S will be converted to a N.
I think there may be a bug in the website parsing.